Architecture for the Automatically Switched Optical Network (ASON) did not appear by accident. Its rise can be attributed to the strike of fast Internet development, the challenges facing operators in providing new value-added services, and the needs of exploring cost-effective networking in the future.
In recent years, information technologies are advancing rapidly, and data services, especially the demands for IP services, are in continuous explosive increase in the backbone network.
With the provision of rich and plentiful services, the requirement for service reliability becomes a primary concern of operators, who expect that services are free from the impact of network exceptions.
The self-healing capability of a network is the key to ensuring that services are not affected in the case of network exceptions. In a traditional network, the protection of services against network exceptions mainly relies on the protection switching of a ring network and the 1+1 or 1:n redundancy of services. The ASON has these traditional protection capabilities with the addition of a service recovery capability. This recovery means protection resources are not reserved in network planning and new services are reestablished only in the event of network exceptions. It can largely increase the efficiency of network resources. Various strategies like segment recovery and preset recovery can be adopted to raise the speed of recovery and minimize the damage to services.
Exceptions in a network come in various forms including fiber break, node failure, node power failure, transmission board failure, service transmission channel failure and node reset. These exceptions are unpredictable. They all require that the network itself is capable of handling upon their occurrence. For fiber breaks and node failures, the ASON has mature solutions. For channel failures, however, no mature solutions are available. Most devices take no action upon a channel (timeslot) alarm and services are in fact interrupted. Therefore, to reduce the impact on services, when an intelligent device suffers a channel failure, recovery means need to be adopted for services running on this channel.
The Link Management Protocol (LMP) provides a specialized link failure location mechanism. The mechanism is activated by a downstream node that detects a data link failure. It checks the link status hop by hop along the Label Switched Path (LSP) through the exchange of channel failure messages and response messages, until the failed link is located.
Based on the exchange of LMP messages including Channel Status, Channel Status ACK, Channel Status Request, and Channel Status Response and the indication of port failure status, this LMP failure handling process can locate a failed port in the ASON. Here, the channel is only specific to ports at present. After a failure is located, recovery methods like rerouting are applied to clear the failed link and protect services.
The prior art enables the location of internal channel failures in a network by extending the port level failure location method in LMP to channel level failure location.
The aforesaid solution, however, is implemented by the exchange of a large number of messages, which not only affects the speed and accuracy of failure location, results in low efficiency in clearing failures and leads to serious service damages, but also hinders the work capability of equipment and harms the network performance.